(1) Field of the Invention
The present invention relates to an exothermic device and an application pad using the same, and more particularly to an exothermic device and a pad using the same, which are capable of eliminating various harmful effects due to an exothermic reaction or coagulation of an exothermic composition occurring in time of manufacture, in particular, which are ultra-thin, have a uniform thickness, and are soft and readily conformable to any curved areas of the human body or the like, which readily follow expansions and contractions of a surface of the human body or the like, and which are free from movement of the exothermic composition during use to give a comfortable feel to the wearer.
(2) Description of the Related Art
In recent years, exothermic devices each having an exothermic composition enclosed between two films or sheets at least one of which is gas-permeable have become widespread as warming devices called disposable body warmers. Some exothermic devices forming the disposable body warmers have an adhesive layer formed on one surface thereof to be applied to the human body or the like. The exothermic devices with a warming effect are increasingly used as applied pads to promote metabolism such as blood circulation or to facilitate absorption of skin absorbable medicine (see Patent Laying-Open Publication No. 2-149272).
Most of the conventional exothermic devices are manufactured by a method based on a technical concept of enclosing an exothermic composition, which generates heat through a reaction with oxygen in the air, in a flat gas-permeable pouch, so that the exothermic composition may be applied directly or through clothing such as underwear to a surface of the human body or the like.
Specifically, according to this manufacturing method, the exothermic composition is injected to fill into a flat inner pouch formed of films or sheets at least one of which is gas-permeable, with three sides closed and one side open, and then the open side is sealed. Alternatively, the exothermic composition is placed on a gas-permeable film or sheet, and then the film or sheet is formed into a pouch with three sides sealed or four sides sealed. The pouch is thereafter inserted into a gastight outer pouch.
The exothermic composition is prepared by mixing a metal powder acting as an exothermic substance, a carbon-containing substance such as carbon powder acting as an exothermic promoter, a chloride and water acting as a reaction promoter (reducing agent), and a water retainer to prevent stickiness. In a traditional manufacturing method, all of these ingredients are blended and then filled into a pouch or placed on a film or sheet which is subsequently formed into a pouch.
As these ingredients are blended in air, an exothermic reaction of the exothermic composition with the oxygen in air is started when all of the ingredients thereof have been blended, and the coagulation of the composition will be started and proceeded in the process of the exothermic reaction.
This gives rise to the problem that, after preparation of the exothermic composition and before insertion thereof into the outer pouch, heat is generated to constitute a heat loss which is not utilized by a wearer of the exothermic device, resulting in a lowering of quality.
A filling apparatus for filling the exothermic composition into the pouch, or a feeding apparatus for feeding the exothermic composition onto a film or sheet, includes a hopper for storing the exothermic composition, and a chute connected to a lower position of the hopper. The exothermic composition of a predetermined quantity is injected into every pouch, or intermittently on a film or sheet running at a speed in the atmosphere.
When the quantity of the exothermic composition in the hopper is decreased below a predetermined quantity, a preferable amount of the exothermic composition blended by a mixer beforehand is replenished, or ingredients of the composition are replenished in the hopper and blended therein.
It is therefore very difficult to maintain the interior of such apparatus shielded from the atmosphere. The exothermic composition may undergo an exothermic reaction or coagulation inside the hopper or chute of the apparatus, often disrupting manufacture or causing quality variations.
Furthermore, before a noon recess and closing of work for the day, the filling apparatus or feeding apparatus must be stopped after the exothermic composition has been exhausted therefrom in order to avoid coagulation of the exothermic composition in the apparatus. Besides, it is necessary to carry out operations, after the exothermic composition is exhausted from the apparatus, to seal the filling apparatus or feeding apparatus and to remove any reaction product adhering to the filling apparatus or feeding apparatus.
The operation for removing the reaction product operation must deal with dust adhering to and remaining on the walls inside the hopper and chute. Thus, the operation is an irksome and ugly operation involving scraping with knives and cleaning with water.
Moreover, if such a removal operation was not carried out before a noon recess or after closing of work, the exothermic composition is maintained in a sealed condition in the filling apparatus or feeding apparatus till commencement of work in the following day, but the exothermic composition solidifies under gravity or undergoes a reaction through contact with air or the like inside the hopper. As a result, the exothermic composition partly coagulates, thereby to bring about variations in the feed and fluidity of the exothermic composition.
Incidentally, sealing of the hopper ordinarily is not more than closing the hopper with a lid. Some air will enter through gaps around the lid to cause coagulation of the exothermic composition. Consequently, clogging of the filling chute or feeding chute is encountered repeatedly, almost every morning.
In addition, the exothermic composition cannot be stored in the filling apparatus or feeding apparatus over a long period of production downtime occurring with introduction of a five-day week or at the year-end to new year holiday, summer holiday, or other consecutive holidays. It is therefore necessary to dispense the exothermic composition in the filling apparatus or feeding apparatus or thoroughly remove it by washing or cleaning. Moreover, the exothermic composition removed from the apparatus by washing or cleaning has already undergone a change in composition and ingredient. Such exothermic composition is not preferable to reuse and must be discarded, thereby resulting in a low yield. Besides, as it is distinct from ordinary wastes, this waste must be treated as so-called industrial waste which involves a high cost of treatment.
Furthermore, a mixer for mixing the ingredients of the exothermic composition tends to be wet with moisture in the compound. Thus, the ingredients of the compound tend to adhere thereto and tend to coagulate through the reaction. It is therefore necessary to carry out an irksome and ugly operation after closing of work every day, which includes scraping with knives and cleaning with water. A considerable amount of adhering matter must be discarded as industrial waste.
Besides, the manufacturing apparatus must have mounted therein a device for preventing bridging of the exothermic composition. Thus, the apparatus is complicated and expensive. There is a further disadvantage that, with filling or feeding of the exothermic composition, dust scatters to the ambient to pollute the working environment.
In the conventional method in particular, the exothermic composition is injected into a flat inner pouch formed of films or sheets at least one of which is gas-permeable, with three sides closed and one side open, and then the open side is sealed. Alternatively, the exothermic composition is scattered on a gas-permeable film or sheet, and then the film or sheet is formed into a pouch. Since, with this method, the exothermic composition having a water content is injected into or scattered on the gas-permeable film or sheet, it is difficult to secure a uniform thickness, which results in serious problems such as variations in temperature distribution.
Besides, it is difficult with the conventional method to form the water-containing exothermic composition injected into or scattered on the gas-permeable film or sheet, to be thin below a predetermined value of thickness. That is, the exothermic composition is formed thick so that it has difficulties in conforming to a complicated curve of a body surface or a curved surface of small curvature and in following expansions and contractions and changes in the shape of a body surface. It also gives a stiff feel.
In addition, since, with this method, the exothermic composition having a water content is injected into or scattered on the gas-permeable film or sheet, not only the exothermic composition is easy to move within the pouch, but the exothermic device is made thick and the exothermic composition tends to move within the pouch. Consequently, the exothermic composition in the pouch tends to be moved during use or during transport.
Incidentally, an ultra-thin, soft, sheet-like exothermic device with ease of temperature control is desired to be made available in the medical field in the future.
There is a strong demand especially for an exothermic sheet formed as ultra-thin as possible to be used as an exothermic device for skin absorption of medicine. With the conventional exothermic composition having all ingredients mixed together, the powdery mixture becomes granulated to form an unsmooth exothermic device. The resulting disadvantages are not only poor adhesion to the skin, but variations in the exothermic composition per se which result in variations in temperature distribution.
Conventionally, a movement of the exothermic composition is prevented by controlling gas-permeability of a porous film to decompress the interior of the covering. However, since the exothermic device per se is thick and the exothermic composition tends to move as noted above, the exothermic composition may be moved in the presence of pinholes in the covering or pinholes formed in time of heat sealing. Just before the end of a exothermic action, the degree of decompression in the covering is lowered, i.e. the covering interior approaches atmospheric pressure, whereby the exothermic composition moves to one side within the covering. A maldistribution occurs also when the heat of the exothermic device exceeds a fixed temperature.
Further, the exothermic composition becomes compact and hard since the interior of the covering is decompressed during use of the exothermic device. Consequently, when it was applied directly to the skin, it gives an unsmooth feel and causes trouble due to skin stress.